feat: add application log ingestion with OpenSearch storage

Agents can now send application log entries in batches via POST /api/v1/data/logs.
Logs are indexed directly into OpenSearch daily indices (logs-{yyyy-MM-dd}) using
the bulk API. Index template defines explicit mappings for full-text search readiness.

New DTOs (LogEntry, LogBatch) added to cameleer3-common in the agent repo.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

HOWTO.md

@@ -100,7 +100,7 @@ JWTs carry a `roles` claim. Endpoints are restricted by role:
 
 | Role | Access |
 |------|--------|
-| `AGENT` | Data ingestion (`/data/**`), heartbeat, SSE events, command ack |
+| `AGENT` | Data ingestion (`/data/**` — executions, diagrams, metrics, logs), heartbeat, SSE events, command ack |
 | `VIEWER` | Search, execution detail, diagrams, agent list |
 | `OPERATOR` | VIEWER + send commands to agents |
 | `ADMIN` | OPERATOR + user management (`/admin/**`) |
@@ -220,6 +220,20 @@ curl -s -X POST http://localhost:8081/api/v1/data/metrics \
   -H "X-Protocol-Version: 1" \
   -H "Authorization: Bearer $TOKEN" \
   -d '[{"agentId":"agent-1","metricName":"cpu","value":42.0,"timestamp":"2026-03-11T00:00:00Z","tags":{}}]'
+
+# Post application log entries (batch)
+curl -s -X POST http://localhost:8081/api/v1/data/logs \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer $TOKEN" \
+  -d '{
+    "entries": [{
+      "timestamp": "2026-03-25T10:00:00Z",
+      "level": "INFO",
+      "loggerName": "com.acme.MyService",
+      "message": "Processing order #12345",
+      "threadName": "main"
+    }]
+  }'
 ```
 
 **Note:** The `X-Protocol-Version: 1` header is required on all `/api/v1/data/**` endpoints. Missing or wrong version returns 400.
@@ -361,6 +375,8 @@ Key settings in `cameleer3-server-app/src/main/resources/application.yml`:
 | `security.oidc.client-secret` | | OAuth2 client secret (`CAMELEER_OIDC_CLIENT_SECRET`) |
 | `security.oidc.roles-claim` | `realm_access.roles` | JSONPath to roles in OIDC id_token (`CAMELEER_OIDC_ROLES_CLAIM`) |
 | `security.oidc.default-roles` | `VIEWER` | Default roles for new OIDC users (`CAMELEER_OIDC_DEFAULT_ROLES`) |
+| `opensearch.log-index-prefix` | `logs-` | OpenSearch index prefix for application logs (`CAMELEER_LOG_INDEX_PREFIX`) |
+| `opensearch.log-retention-days` | `7` | Days before log indices are deleted (`CAMELEER_LOG_RETENTION_DAYS`) |
 
 ## Web UI Development